Method of treating cut film



@Ch 9 1934 H. E. VAN DERHOF METHOD 0F TREATING CUT FILM Filed NOV. 13, 1929 mw N L.: RQQQ MMSE@ m @Il aucun,

Patented ct.

1,976,311 tm'rnoi) or'rnaarind cU'r FILM Application November 13, 192,9, Serial No. 406,886

7 Claims.

This invention relates to photography, and more particularly to photographic film.

One of the objects of my invention is to provide a nlm or other cellulose derivative products, the 5 durability of which is greatly increased. Another object is to lessen the cracking and tearing of the film during use. Still another Objectis to reduce, if not practically eliminate, the amount of edge shrinkage of the film. A further object is to obtain said durability and reduce said edge shrinking of the lm Without interfering with the normal motion of the nlm on the customary sprocket and other film advancing devices. Other objects will appear in the following specification, the novel features being pointed out in the claims appended at the end thereof.

In the drawing, wherein like reference characters denote like parts throughout:

Fig. 1 is a diagrammatic elevation on an enlarged scale of one section of apparatus used in my invention;

Fig. 2 is a diagrammatic elevation of another section of apparatus used in my invention.

When motion picture films are repeatedly pro- 15,125 'jected, they become cracked and torn so that they cannot be further used. It is highly desirable to increase the durability of the film both against cracking and tearing from repeated projection.

Another great difficulty is caused by a shrinking of the edges of the film in excess of the body or portion between said edges. If a full width roll of film has been allowed to stand for some time, a decided shrinkage of the edge portions is noticeable, so that when said film is run over a coating machine, the center of the sheet will not touch the dryers snugly. In the handling of motion picture film this edge shrinkage proves troublesome in the registration of the picture frames when printing and in driving the nlm by any of the customary methods.

I have found that said cracking and tearing of the film is greatly aided and caused by the raw out edges of the film for two reasons. First, the cut edges consist of innumerable marks and cuts due to the rough edge of the cutting instrument, these breaks are quickly enlarged and spread by the usual wear received by the ordinary film. Secondly, these raw edges allow the solvents in the film to evaporate much more rapidly than do the l'50 surfaces of the film, causing said film to become brittle and increasing the ease with which it tears.

The raw edges are also the principal cause of the fast shrinking of the edge portions of the film. The evaporation of the solvents which causes the film to get brittle also causes it to shrink.

(ci, ias- 57) I have found that these difficulties may be overcome in a very large and unexpected amount by curing or removing the rawness of the edges of the lm or other cellulose derivative products` I propose to apply a small amount of some solvent to v: the raw edges to partially dissolve them so that when they dry they will have a smooth, even surface such as the outer surface of the lm. This also increases the ease of handling the film.

To apply this solvent I may employ an apparatus such as disclosed in the drawing. The apparatus shown in Figure l, used to apply the solvent to the outside edges of the film, comprises a pair of grooved rollers 1 which fit snugly against the edges lo of the film 2, said rollers having a supply 70 of solvent 3, which is brought into contact with said edges 10. The solvent 3 is supplied to rollers i by the endless belt 4 which runs through a trough or tank 5 containing said solvent 3. The belt 4 may be driven by the rollers 6 which holds said .75 belt 4 in contact with the supply rollers 1. The supply rollers 1 may be driven by the gear train '7 and the belt 8 and pulley 9, or they may idle, and receive their motion by friction with the lm 2.

The apparatus in Figure 2, to apply said Solvent E 3 to the edges of freshly formed perforations in motion picture film, comprises a sprocket wheel 2l having sprocket teeth 22 which are dipped into a tank 24 containing the solvent 3, and carrying said solvent 3 to the perforations 23 of the film 2. T85 The supply rollers 1 and the sprocket wheel 21 and teeth 22 should be made of some material which will retain the wetted condition and which will not be affected by the solvent 3. This material should either be metal, hard rubber, bake-F lite,'or possibly felt.

The solvent is applied to the raw edges of either nitrate or acetate film or other cellulose derivative products such as a sheet, rod, slab or the like, tor partially dissolve the edges, then the productsV should be allowed to dry under the natural conditions, allowing the molecules to align themselves on the surfaces in conformity to the surface thus producing a surface skin which is stronger and` ,100 more resistant to wear, said surface skin at the same time retaining the solvents and preventing rapid evaporization and shrinkage.

I have found that the best liquid to use consists of a quick-acting, low-boiling solvent mix-- ture containing, for instance, acetone, ethyl acetate or any similar solvent. If acetone is used,

a small amount of high-boiling solvent such as amyl acetate should be added to restrain rapid evaporation and to prevent the lm from taking on moisture while drying and thus becoming White.

It is to be understood that though I have cited these particular solvents, any other suitable lowboiling solvents and any method of applying said solvents to the lm edges may be used Without departing from the spirit of this invention.

Having thus described my invention, what I claim as new and desire to secure by Letters Patent is:

1. A process for producing film with low shrinking characteristics which comprises cutting a lm element from a large sheet comprising a cellulose derivative, and sealing the cut edges through the application of a solvent to said edges.

2. A process or producing film with low shrinking characteristics which comprises cutting a film element from a large sheet comprising a cellulose derivative, and sealing the cut edges through the application of a solvent, said solvent comprising a quick-acting low-boiling solvent mixture to said edges.

3. A process for producing lm with low shrinking characteristics which comprises cutting a lm element from a large sheet comprising a cellulose derivative, and sealing the cut edges through the application of a solvent comprising acetone and amyl acetate to said edges.

4. The process of preparing a sheet, comprising a cellulose derivative, which comprises forming said sheet by an operation producing cut edges and applying to the cut edges a solvent for the material of the sheet.

5. The process which comprises coalescing with a solvent therefor the cut edge of a cellulose derivative product.

6. The process which comprises coalescing With a solvent therefor the cut edge of a product comprising an organic derivative of cellulose.

7. The process which comprises coalescing with a solvent therefor the cut edge of a product comprising an inorganic derivative of cellulose.

HENRY E. VAN DERHOEF.

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